This invention relates generally to a system and method for measuring process parameters in a process and in particular to a system and method for measuring process parameters in process equipment used during a manufacturing process, including semiconductor manufacturing, disk drive manufacturing, flat panel display manufacturing, medical device manufacturing or electronic component assembly, etc..
One manufacturing area in which process parameters are critical is the semiconductor device manufacturing process. In the semiconductor manufacturing process, one particularly important parameter is the electrostatic discharge (ESD) occurrence parameter (which includes electrostatic discharges or electrostatic voltages). With the advances of semiconductor technology, ESD damage to the semiconductor devices today has become a larger factor in yield losses. There are several objective reasons why ESD damage has become such a large factor in yield losses. The smaller geometries of the semiconductor device structures (such as the gate size or oxide thickness) means higher sensitivity to ESD occurrences (including electrostatic discharge or electrostatic voltage). In particular, it takes much less energy to destroy a trace for a device on a die with a 0.10μ geometry than for a device with an older 0.25μ geometry. Furthermore, conventional well known ESD protection measures that are built into the devices are not fully compatible with high-speed signals. In particular, the relatively high parasitic capacitance of the ESD protection measures substantially affects slew rate and rise and fall time of pulses at high speeds. Smaller-capacitance ESD protective devices might affect high-speed signals to a lesser degree, however they offer much less protection against ESD. Radio frequency (RF)/MMIC integrated circuit devices (ICs) cannot afford to have the level of ESD protection that is common for digital ICs. FIG. 1 shows the changing ESD sensitivity for different semiconductor technologies. As shown, power integrated circuits (ICs) have a much lower level of ESD sensitivity (are able to handle approximately 1000 volts without failing) than high-speed ICs, which in turn have less sensitivity to ESD than RF ICs.
The increased number of I/O pins on modern ICs statistically increases the probability of IC failure. Furthermore, the larger die sizes used today make losses more expensive. In addition, integrated circuits exposed to one or more ESD occurrences (including electrostatic discharge or electrostatic voltage) may not fail right away, but the latent damage causes losses and alienates customers.
Modernly, there is an increasing pressure to reduce the cost of each IC. The handling time for each IC accounts for some portion of the cost of the IC. Therefore, to reduce costs, handling time is reduced which results in the ICs being moved faster through the manufacturing process. The result of the more rapid processing of the IC are that static voltage is accumulated extremely fast. In addition, the conventional ionizers cannot handle such rapid movement since it takes several seconds for an ionizer to discharge IC to a safe voltage level. In these few seconds that it takes the ionizer to properly discharge the unwanted voltage, several ICs will be tested and moved away from the test area. The only feedback as to whether or not the ionizer is operating properly is the yield figure so that the problem cannot be corrected until after a lot of semiconductor devices are lost.
The most damaging discharges often occur after the IC was tested (e.g., when the IC leaves the test socket, when the IC is placed on the exit shuttle and when the IC is placed onto the exit tray). In all these cases, a manufacturer has no knowledge of IC damage and can unknowingly ship defective products to a customer. While it is nearly impossible to completely avoid ESD exposure of sensitive components, it is possible to identify steps in the process that are responsible for ESD damage and to identify and isolate exposed components. Thus, Event monitoring offer various benefits to a semiconductor manufacture. Event monitoring will allow the manufacturer to isolate ESD occurrences, to identify exposed parts and to alert personnel to the ESD problems so that the ESD problems may be corrected. Event monitoring also will provide valuable statistics to the manufacturer, become part of the SPC, identify the most vulnerable steps in the process and ultimately assure that no IC exposed to ESD and damaged by the ESD is shipped to a customer.
The most dominant type of discharge of concern in an IC handler is CDM (Charge Device Model). CDM events are characterized by the following critical parameters including a very short rise time, a very short duration and a very high magnitude. The damage caused to the device by the discharge is a function of the power of the discharge, i.e. the rate of influx of energy into device. Therefore, in order to assess the ESD exposure of a device, it is important to monitor the rise time of the discharge, the duration of the discharge and the magnitude of the discharge and not only the peak magnitude of discharge ESD occurrences (including electrostatic discharge or electrostatic voltage) are detected by measuring electromagnetic radiation produced by the discharge. The specific properties of the emission generated by ESD occurrences (including electrostatic discharge or electrostatic voltage) include very short pulse duration (in the nanosecond range), rapid rise time (under 500 picoseconds for CDM-type discharges) and wide bandwidth. Event Monitors are tuned to these and other unique electromagnetic properties of ESD occurrence and are capable of measuring strength of each individual ESD occurrence and also of resolving multiple ESD occurrences (including electrostatic discharge or electrostatic voltage) that are common in production environment.
It is desirable to have an process parameter event monitoring system and method that is able to monitor the ESD occurrences (including electrostatic discharge or electrostatic voltage) for each machine in the semiconductor process so that ESD occurrences (including electrostatic discharge or electrostatic voltage) are detected quickly and corrected. It also is desirable to provide a system and method that is capable of monitoring other process parameters, such as pressure, temperature, etc. in other processes, including but not limited to disk drive manufacturing, flat panel production, medical device manufacture, electronic assembly, etc. Thus, it is desirable to provide an process parameter event monitoring system and method that measures various process parameters of various different manufacturing processes and it is to this end that the present invention is directed.